1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine, a laser beam printer (hereinafter referred to as “LBP”), and a facsimile machine, which includes an original read apparatus as typified by an automatic document feeder (hereinafter referred to as “ADF”) unit.
2. Description of the Related Art
Conventionally, in this type of image forming apparatus, an original conveyance path of the original read apparatus and a recording material conveyance path of an image forming unit are provided independently of each other. Specifically, a sheet feeding unit for an original or a recording material, a guide member serving as a predetermined conveyance path, multiple conveyance rollers, a drive force transmission unit for the conveyance rollers, a motor serving as a drive source, a driving circuit of the motor, a sheet discharging unit, and other components are arranged in each of the original conveyance path and the recording material conveyance path.
Such arrangement inevitably leads to complication of the overall mechanism configuration of the image forming apparatus and increase in cost and size thereof. To solve those problems, for example, Japanese Patent Application Laid-Open No. 2006-232467 discloses an original read unit arranged in a double-sided conveyance path of the recording material, which extends from the sheet feeding unit to the sheet discharging unit, to thereby use one common path for both the original conveyance system and the recording material conveyance system. Thus, a simple configuration and reduction in cost and size of the image forming apparatus are attained.
In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2006-232467, however, the original read unit is arranged in the double-sided conveyance path of the recording material, and hence, when the original is present in the double-sided conveyance path, the double-sided print operation cannot be executed. Therefore, during the original read operation, the print operation needs to be stopped, and as a result, the productivity decreases when printing an image of the original that has undergone the read operation. Further, a recording material as well as the original passes across an original read surface of the original read unit, and hence the original read surface is liable to be blotted. Still further, a time period to correct a white reference value of the original read unit is limited. As a result, stable print performance cannot be obtained.